Electricity: conductors and insulators – Conduits – cables or conductors – Preformed panel circuit arrangement
Patent
1996-10-30
1999-03-09
Sough, Hyung-Sub
Electricity: conductors and insulators
Conduits, cables or conductors
Preformed panel circuit arrangement
174258, 204426, H05K 100, G01N 2726
Patent
active
058804064
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a cover layer on at least one electrical conductor and/or semiconductor, especially of an electric sensor.
Cover layers for electrical conductors are known (DE-23 04 464 C2). They consist for example of barium-aluminum silicates, applied using the usual methods employed in ceramics technology. Such coatings are generally gas-tight cover layers.
In addition, porous cover layers are also known that consist for example of a metal, a metal alloy, an oxide, or a mixed oxide such as magnesium spinel, carbides, borides, nitrites of transition metals, or silicate minerals such as high-melting sintered glass or fireproof ceramic materials for example, which can also be applied as raw materials or mixtures of raw materials such as kaolin or talc, possibly with the addition of fluxes such as feldspar, nepheline syenite, or wollastonite, and then sintered.
In known protective layers, the gas-tight cover layer is applied to a solid electrolyte, while the porous first protective layer is located above the electrodes.
It has been found that when electrical conductors are covered with gas-tight cover layers, ions such as calcium, sodium, or oxygen ions migrate under the influence of the electrical voltages applied to the conductors, especially at higher temperatures, causing damage in the first protective layer and consequently in the conductors as well. In addition, discharges of oxygen ions can also release oxygen bubbles.
SUMMARY OF THE INVENTION
The goal of the present invention is to create cover layers in which ion migration is reduced in normal operating states.
In the cover layers according to the invention, a porous first protective layer is located directly on the surface of the electrical conductor and/or semiconductor and a gas-tight second protective layer is located at least areawise on the porous first protective layer.
Surprisingly, oxygen ion migration can be reduced by applying the porous first protective layer beneath the gas-tight second protective layer on the surface of the electrical conductor or semiconductor. As a result, the migration of oxygen ions between conductors with different potentials, and hence their harmful influence, can be reduced. In this connection it is theoretically immaterial whether the porous first protective layer is made with open or closed pores, although the open-pored state is more advantageous. If on the other hand the porous first protective layer is to be used to cover the electrodes and/or gas-sensitive layers of electrical sensors that measure gas, open-pored porosity is essential. The porous first protective layer contains 20 to 60 parts by weight of silicon dioxide, 28 to 75 parts by weight of aluminum oxide, and 1 to 27 parts by weight of barium oxide.
The gas-tight second protective layer contains 20 to 56 parts by weight of silicon dioxide, 28 to 75 parts by weight of aluminum oxide, and 2 to 55 parts by weight of barium oxide.
The first porous protective layer preferably contains 28 to 50 parts by weight of silicon dioxide and 30 to 65 parts by weight of aluminum oxide. The addition of barium oxide preferably is on the order of 2 to 20 parts by weight.
The gas-tight second protective layer preferably contains 28 to 50 parts by weight of silicon oxide and 30 to 65 parts by weight of aluminum oxide. The barium oxide content is on the order of 4 to 50 parts by weight of barium oxide. The porosity of the two protective layers can be controlled by the barium oxide content. The gas-tight second protective layer has a barium oxide content that is generally 2 to 8.5 times greater than that of the porous first protective layer.
The gas-tight second protective layer especially preferably contains 30 to 45 parts by weight of silicon dioxide, and especially 35 to 40 parts by weight of silicon dioxide. The aluminum oxide content of the gas-tight second protective layer is advantageously in the range from 30.0 to 65.0 parts by weight, especially preferably in the range from 40.0 to 60 parts by weight, and espec
REFERENCES:
patent: 3978006 (1976-08-01), Topp et al.
patent: 4296148 (1981-10-01), Friese
patent: 4943330 (1990-07-01), Iino et al.
patent: 5310575 (1994-05-01), Friese et al.
Gerstel Peter
Schonauer Ulrich
Tafferner Michael
Heraeus Electro-Nite International N.V.
Sough Hyung-Sub
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